OK, I get it - my file size is big because it's linked to the original Photoshop document. I remember reading about linked files in one of the tutorials, but I haven't really experimented with it yet.
I don't understand your last statement:
As I like vector based objects, I would copy all the elements (ctrl+A, ctrl+C) into Photoshop (ctrl+V) and select "Shape layer" (or "Smart Object"), so they could be scaled without the quality loss.
I assume "all the elements" refers to every item in Illustrator, including the outline map and any other items I might have "placed" from Photoshop, right? If I click ctrl+A, ctrl+C, it will automatically copy EVERYTHING in my Illustrator file, after which I can create a new Photoshop file and paste it in. In Photoshop, I can then select "Shape layer" to modify all these items so they can be scaled.
So what you're describing is a way to more or less vectorize objects in Photoshop, right? If the Shaper Layer function makes items scalable in Photoshop, then is there any reason I should learn Illustrator? I have read that text is crisper in Illustrator, though I haven't experimented with that yet. But can the Shape Layer also be applied to text in Photoshop?
Photoshop is actually my preferred program, because I'm familar with it. I'm finding the Illustrator learning curve a little steep, but I thought it would be worth learning because of vectors alone. But if Photoshop's Shape Layer function does the same thing, maybe I should just stick with Photoshop.